1. Field of the Invention
The invention relates to an apparatus for cleaning the outer surface of a cylinder with a cleaning fabric in an offset printing press. The cylinder may be a blanket cylinder, plate cylinder, inking roller and the like. In particular, the invention relates to a pressure pad used in the apparatus. The cleaning fabric is pressed against the outer surface of the cylinder by the pressure pad to clean the outer surface of the cylinder. In addition, the apparatus includes main members shaped by metal plate working.
2. Description of Related Art
There has been proposed an apparatus for cleaning the outer surface of a cylinder with a cleaning fabric in an offset printing press, as disclosed in Japanese Laid-Open Patent Publications No. 250,046 of 1998 and No. 143,545 of 1994. The cleaning fabric is directed between a pressure pad and the cylinder. The pressure pad has opposite side edges which are disposed in the apparatus to extend parallel to the cylinder. The pressure pad is made of elastomer to be constant in thickness and rigidness throughout the length and width thereof. In addition, the pressure pad takes the form of an arch which is curved between the opposite side edges thereof to be convex toward the outer surface of the cylinder. The pressure pad cooperates with the cleaning fabric so that the cleaning fabric can be pressed against the outer surface of the cylinder by the pressure pad when the cylinder is rotated, to clean the outer surface of the cylinder.
However, as to a blanket cylinder in the offset printing press, the cylinder includes a gap formed between the opposite ends of a blanket which is wound around the cylinder. The pressure pad is therefore subject to a shock caused by the gap of the cylinder whenever the gap reaches the pressure pad, resulting in noise and vibration, even if the cylinder is rotated at a low speed of about 8 rpm. The noise and vibration are gradually increased in proportion to the rotating speed of the cylinder. The noise and vibration are extremely increased to be unacceptable when the cylinder is rotated at a high speed of about 70 rpm.
There has been also proposed an apparatus including an air pad or expandable bladder, as disclosed in U.S. Pat. No. 4,344,361. In the apparatus, the noise and vibration can be decreased by the air pad. However, the air pad involves a source of air, piping, control of air and the like to be complicated and expensive.
In addition, the apparatus generally includes a support bar to which the opposite side edges of the pressure pad are fixed. A pair of side plates are spaced from and opposed to each other. The support bar extends between the side plates to be mounted directly or indirectly on the side plates for supporting the pressure pad. In the case, it is required to remove the assembly including the support bar, the side plates and the like from adapter plates which are mounted on fixed frame means, occasionally for maintenance. It is also required to then set again the assembly on the adapter plates. However, the support bar has been machined to be rigid, so as not to amplify the noise and vibration of the pressure pad. In this connection, the support bar is considerably heavy. It is therefore troublesome to remove and then set again the assembly, taking labour and time.
It is therefore an object of the invention to provide a new and improved pressure pad used in an apparatus for cleaning the outer surface of a cylinder with a cleaning fabric, to thereby overcome the above problems.
Another object of the invention is to provide the pressure pad in which the cleaning fabric can be conveniently pressed against the outer surface of the cylinder by the pressure pad without being complicated and expense, to clean the outer surface of the cylinder.
Other object of the invention is to provide the pressure pad in which the noise and vibration can be effectively decreased to be acceptable not only when the cylinder is rotated at a low speed but also when it is rotated at a high speed.
Other object of the invention is to provide the apparatus including a support bar to which the opposite side edges of the pressure pad are fixed, the support bar being rigid so as not to amplify the noise and the vibration of the pressure pad.
Other object of the invention is to provide the apparatus in which the support bar is relatively light to remove and then set again the assembly including the support bar and the like without taking labour and time.
3. Summary of the Invention
According to the invention, there is provided a pressure pad used in an apparatus for cleaning the outer surface of a cylinder with a cleaning fabric. The cleaning fabric is directed between the pressure pad and the cylinder, the pressure pad having opposite side edges which are disposed in the apparatus to extend parallel to the cylinder. The pressure pad is made of elastomer and curved between the opposite side edges thereof to be convex toward the outer surface of the cylinder. The pressure pad cooperates with the cleaning fabric so that the cleaning fabric can be pressed against the outer surface of the cylinder by the pressure pad to clean the outer surface of the cylinder.
The pressure pad comprises an engaged portion engaged with the cleaning fabric so that the cleaning fabric is sandwiched between the engaged portion and the cylinder to be pressed against the outer surface of the cylinder. The pressure pad further comprises a pressure imparting portion positioned between the engaged portion and at least one of the opposite side edges of the pressure pad for imparting a pressure between the engaged portion and the cylinder. The pressure imparting portion is different in mechanical parameter from the engaged portion.
The mechanical parameter may comprise the thickness of the pressure pad. In the embodiment, the engaged portion is relatively thin. The pressure imparting portion is relatively thick to be different in thickness from the engaged portion.
The pressure pad may include a central portion intermediate between the opposite side edges of the pressure pad. In addition, the pressure pad may vary in thickness to be more thick toward the opposite side edges from the central portion. In the embodiment, the engaged portion comprises the central portion. The pressure imparting portion comprises the more thick portion positioned between the central portion and at least one of the opposite side edges. The pressure pad may vary in thickness continuously. The pressure pad may vary in thickness discontinuously.
The pressure pad may vary in thickness to be more thick toward one of the opposite side edges of the pressure pad from the other side edge. In the embodiment, the engaged portion comprises a relatively thin portion spaced from the opposite side edges. The pressure imparting portion comprises the more thick portion positioned between the relatively thin portion and one of the opposite side edges. The pressure pad may vary in thickness continuously. The pressure pad may vary in thickness discontinuously.
The mechanical parameter may comprise the rigidness of the pressure pad. In the embodiment, the engaged portion is relatively flexible. The pressure imparting portion is relatively rigid to be different in rigidness from the engaged portion. The pressure imparting portion may include fibers incorporated thereinto to be relatively rigid.
The apparatus may comprise a pair of side plates spaced from and opposed to each other. The apparatus may further comprise a support bar to which the opposite side edges of the pressure pad are fixed. The support bar extends between the side plates to be mounted directly or indirectly on the side plates for supporting the pressure pad. The support bar may comprise a metal plate which includes at least one bend formed by metal plate working.
The apparatus may further comprise a supply of cleaning fabric from which the cleaning fabric is supplied to the pressure pad. Support means may be mounted on the side plates for supporting the supply of cleaning fabric. A take-up shaft may extend between the side plates to be mounted on the side plates for removal, the cleaning fabric being directed to the take-up shaft through the pressure pad. First drive means may be provided for rotating the take-up shaft to take-up the cleaning fabric about the take-up shaft. The apparatus may further comprise adapter plate means mounted on fixed frame means and including guide means for supporting and guiding the side plates for movement toward and from the cylinder. Second drive means may be connected directly or indirectly to the side plates for moving the side plates along the guide means toward and from the cylinder so that the cleaning fabric can be pressed against and retracted from the cylinder.
According to the invention, there is also provided the apparatus in which the support bar extends between the side plates to be mounted directly or indirectly on the side plates for supporting the pressure pad, the support bar comprising the metal plate which includes at least one bend formed by metal plate working.
The pressure pad may comprise an air pad, a sponge pad or an elastomer pad having a constant thickness.
The supply of cleaning fabric may comprise a supply roll including a core about which the cleaning fabric is wound. The supply roll may further include projections projecting from the opposite end surfaces of the supply roll. The support means may comprise metal plates shaped by metal plate working to include slots into which the projections are received for movement in accordance with the decrease in diameter of the supply roll.
The support means may be integrally fixed to the support bar to be mounted indirectly on the side plates.
The support bar may include a pressure pad support portion for supporting the pressure pad and a supply roll support portion bended from the pressure pad support portion by the bend. The supply roll may have an outer surface engaged with the supply roll support portion to support the supply roll for rotation.
A movable member may be engaged with the outer surface of the supply roll. Resiliently urging means may be provided for resiliently urging the movable member to move it in accordance with the decrease in diameter of the supply roll.
The first drive means may rotate the take-up shaft in response to the second drive means moving the side plates by which the cleaning fabric is pressed against and retracted from the cylinder.
The first drive means may comprise a handle connected to the take-up shaft through a one-way clutch to manually rotate the take-up shaft an angle at a time.